The present invention relates to an automatic image developing apparatus for a silver halide photographic photosensitive material, and more particularly to an automatic image developing apparatus for automatically developing an image on a silver halide photographic photosensitive material after it has been exposed or the image has been recorded thereon by feeding the photosensitive material successively through developing, fixing, and washing tanks, the automatic image developing apparatus being capable of saving as much washing water as possible which is to be supplied to the washing tank, of preventing processing chemicals from being transferred to the photosensitive material thereby to avoid contamination of the image, and of storing the developed photosensitive material for a long period of time.
Radiation image recording systems are widely used in the medical field for obtaining information on affected parts of patients. In such a radiation image recording system, a patient to be examined is exposed to radiation, and obtained radiation image information is recorded on a film of silver halide black-and-white photographic photosensitive material. Then, the photosensitive film with the image recorded thereon is fed into an automatic image developing apparatus.
In the automatic image developing apparatus, the film is first delivered into a developing tank containing a developing solution, and then passed through a fixing tank containing a fixing solution, after which the film is put into a washing tank containing washing water. Then, the film is passed through a squeezing unit having rollers which squeeze water out of the film, and delivered into a drying unit in which hot air at a temperature ranging from about 50.degree. C. to 55.degree. C. is applied to the film to dry the same. Subsequently, the film is stored in a prescribed storage location and will be used for medical diagnosis or the like when required.
The water tank is disposed in the automatic image developing apparatus for washing the film that has been immersed in and passed through the developing and fixing solutions, as described above. The washing tank is supplied at all times with a large amount of washing water (for example, 3 liters or more of washing water for 1 m.sup.2 of the photosensitive material) to keep the water in the washing tank clean.
However, supplying the washing tank with a great amount of washing water at all times is highly uneconomical and does not meet recent growing demands for the saving of resources.
If the amount of water to be supplied to the washing tank were to be considerably reduced, washing water would be left stagnant in the washing tank over a long interval of time, forming bacterial slime in the water or permitting the water to be rotten to give off an ill odor. If the automatic image developing apparatus were stopped in operation for several consecutive days, floating matters would form in the washing water, and would tend to attach to the film or clog a filter in the apparatus when the apparatus is started again. To avoid the above problems, the wahing tank would have to be cleaned periodically, and such a cleaning process would be time-consuming and would exert an undue burden on the worker.
Various automatic image developing apparatus have heretofore been proposed for effectively waving washing water to be supplied to the washing tank. One example is a countercurrent washing process which employs a multiplicity of washing tank. More specifically, a plurality of washing tanks are disposed at different vertical levels in a step-like configuration, and a relatively small amount of washing water is supplied from the uppermost washing tank successively to the other lower washing tanks. At the same time, the film to be developed is washed by being successively immersed in and passed through the washing tanks.
With the automatic image developing apparatus of the aforesaid construction, however, a plurality of washing tanks are required, and so are feed rollers and racks associated with the respective washing tanks. As a result, the overall automatic image developing apparatus is large in size and fails to effectively utilize a space for image developing operation. This automatic image developing apparatus is also disadvantageous in that the cost of manufacture of the apparatus is very high.
In view of the aforesaid shortcomings, there have been proposed various image developing processes capable of preventing washing water from being rotten or preventing bacterial slime from forming in washing water thereby to greatly reduce the about of washing water to be supplied to the washing tank by adding a chelating agent or a biocide such as a halide (see Japanese Patent Applications Nos. 60-253807 and 61-30305, for example). With these proposals, films can be washed for a long period of time even in a reservoir-type washing tank without increasing the size of the automatic image developing apparatus and while saving as much washing water as possible.
When washing a film with a reduced amount of washing water or a pool of washing water rather than a large amount of running washing water, thiosulfate and the like, for example, of the fixing solution are progressively delivered via the film and accumulated in the washing water in the washing tank as the developing process progresses. When the film is squeezed after it has been washed, therefore, thiosulfate and the like are squeezed out by the squeezing rollers and are often attached to these rollers. The squeezing unit is located closely to the drying unit.
While the developing process is being intermittently carried out, therefore, the squeezing rollers are rapidly dried by hot air from the drying unit when the developing process is not effected. At this time, thiosulfate is deposited in an irregular pattern and at a high density on the roller surfaces. If the washed film were fed by these rollers again, thiosulfate deposits would be attached to localized areas of the film surface, resulting in image density irregularities or surface reflection irregularities, or the localized film areas would be yellowed by such thiosulfate deposits during storage of the developed film over a long period of time.